This invention relates in general to doors and more particularly to a door closer provided with means for indicating the position of the door.
At some door openings it is neither desirable nor possible to mount the door, which normally closes the opening, on conventional leaf-type hinges. For example, many modern buildings have doors which are substantially all glass. These doors contain a large thick slab of glass which extends from one side edge of the door to the other. Obviously, hinges cannot be secured directly to the glass. Normally, the upper and lower ends of the glass slabs are capped with metal rails and the lower rail is supported on the spindle of a door closer, whereas upper rail is connected to a top pivot which is mounted on the lintel piece of some other member extended over the door opening.
Moreover, many buildings of the modern construction utilize electrically operated surveillance systems instead of watchmen to detect and discourage unauthorized entries. These systems actually maintain surveillance over doors at critical locations in the buildings and signal an alarm when any one of the doors is opened, even momentarily, at a time when it should not be. Heretofore, devices have been incorporated into hinges for closing an alarm circuit when the hinge leaves part and hence detecting the opening of the door hung with such hinges. The Switch Hinge of U.S. Pat. No. 3,715,537, the Contact Hinge of U.S. Pat. No. 3,659,063, and the Interrupted Slip Ring Hinge of U.S. Pat. application Ser. No. 375,788, filed July 2, 1973, are all capable of making and breaking an electrical circuit in response to movement of the hinge leaves and hence are suitable for use in surveillance systems for hinge hung doors. These hinges completely obscure the electrical circuitry and circuit interrupting means when the door is closed and cannnot be tampered with by potential intruders. However, no tamper-proof arrangement has been developed for doors supported on so-called door closers.
Aside from the foregoing, it is often necessary to ascertain when a door is precisely in its closed position so that a bolt may be thrown from a remote location to secure the door. Again, hinges have been developed which provide the foregoing determination in the case of hinge hung doors, but not for closer mounted doors.